A US soldier has killed more than a dozen civilians in a shooting spree in southern Afghanistan before being detained, officials say.

A member of the Kandahar provincial council who visited the site of the shooting in Panjwai district told Al Jazeera that at least 17 civilians were killed when the soldier left his base early on Sunday morning and opened fire.

Captain Justin Brockhoff, a spokesman for the NATO-led International Security Assistance Force (ISAF) could not confirm any fatalities in the incident.

“This is a horrific incident, and our thoughts are with the families of the affected. Our initial reports indicate multiple civilians - between four and six- are wounded. Those civilians are receiving care at coalition medical facilities," he told Al Jazeera.

"At this point we do not have an indication - we can not speculate about the individual's motives."

Sediq Seddiqi, the spokesman for the Afghan interior ministry, told Al Jazeera the incident was under investigation. He could not confirm any reports of casualties.

l Jazeera's Bernard Smith, reporting from Herat, said the soldier opened fire on civilians around the base.

"We are now being told by the police sources that the US soldier left his base at three o clock this morning. It would have been pitch-black wherever he walked," he said.

Civilian casualties have been a major source of friction between President Hamid Karzai's government and US-led NATO forces in Afghanistan.

Anti-American sentiment had already been running high before news of the latest civilian casualties.

Anger gripped the country after US soldiers burned a large number of copies of the Quran, the Muslim holy book, at a NATO base last month, which NATO said was a tragic blunder.